1. Field of the invention
This invention relates to a process for simultaneously producing methacrylonitrile and butadiene by simultaneously effecting ammoxidation and oxidation of mixed butenes containing as the substantial reactant isobutene and n-butenes in vapor phase.
2. Description of the prior art
Heretofore, efficient simultaneous production of methacrylonitrile and butadiene from mixed butenes containing isobutene and n-butenes by simultaneously effecting ammoxidation and oxidation in vapor phase has been considered to be difficult due to difference in reactivity between isobutene and n-butenes when conducted using one and the same catalyst under common reaction conditions.
A number of processes have recently been proposed for the production of methacrylonitrile from olefins by vapor-phase ammoxidation as well as for the production of butadiene from olefins by vapor phase catalytic oxidation. However, all of these processes involve separative use of isobutylene or n-butenes alone, and there has never been proposed the process for simultaneously producing methacrylonitrile and butadiene by vapor-phase oxidation of mixed butenes. Isobutene and n-butene are separated and purified usually from the B-B fraction (fraction containing a mixture of butanes, butenes and butadiene, namely, C.sub.4 fraction) formed on cracking a petroleum fraction (for example, naphtha or kerosene, or crude oil) or the B-B fraction by-produced in purification of petroleum, and isobutene, 1-butene, cis-2-butene, trans-2-butene and butanes are quite similar in chemical and physical properties. Accordingly, separation and purification to isolate isobutene or n-butenes with a high purity are not easy but are expensive.